private parker watson still has a baby face at 20. but he is a battle-hardened combat medic. when this war began, he was just a little boy. >> were you frightened? >> a little frightened at first, but i was reassured by my parents it would be all right. >> reporter: as watson watched the towers collapse, an even younger boy was there running for his life. >> what do you remember about it? >> the booms. me and my mom running down west side highway to get across the brooklyn bridge. >> did you want to join the army then? >> then? not really. >> reporter: at 18, lee williams joined the army. he is proud to serve like so many his age. >> i can't imagine you ever thought, gee, i'll be over there fighting some day. >> ever since then, i kind of wanted to. >> reporter: captain alex hague, grandson of the former general and secretary of state was a college student in washington on 9/11. >> all my friends are serving. so it's something i think about every day. and it's very much a part of my reality. >> there is another reality for those older soldiers. they have been in two wars now,